Projectile with a rearwardly directed steering tube



Oct. 17, 1967 H. ABRAMSON PROJECTILE WITH A REARWARDLY DIRECTED STEERING TUBE 7 Filed May 19, 1966 4 Sheets-Sheet l H. ABRAMSON Oct. 17, 1967 PROJECTLLE WITH A REARWABDLY DIRECTED STEERING TUBE 1966 4 Sheets-Sheet 2 Filed May 19,

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. PROJECTILE WITH A REARWARDLY DIRECTED STEERING TUBE Filed May 19, 1966 4 Sheets-Sheet 5 PROJECTILE WITH A REARWARDLY DIRECTED STEERING TUBE Filed May 19, 1966 4 Sheets-Sheet 4 United States Patent 3,347,492 PROJECTILE WITH A REARWARDLY DIRECTED STEERING TUBE Hugo Abramson, Eskilstuna, Sweden, assignor to Fiirsvarets Fahriksverk, Eskilstuna, Sweden, a corporation of Sweden Filed May 19, 1966, Ser. No. 551,343 Claims priority, application Sweden, June 14, 1965, 7,836/ 65 4 Claims. (Cl. 244-328) ABSTRACT OF THE DISCLOSURE A projectile having a steering tube at its rear end, the tube having a plurality of longitudinally extending slots directed forward from the rear end of the tube, thereby dividing the tube at its rear end, into a plurality of separate flaps. Transverse slots are provided in the tube, such transverse slots being in the form of V-shaped notches, there being one of these V-notches in the tube at the base end of each of the flaps and the transverse V-notches are substantially in line with inner ends of the longitudinal slots. The flaps are bent outwardly on the line of the transverse slots When the projectile is fired and the outward movement of the flaps is limited since such movement is halted at a predetermined point by contact between the walls of each of the V-shaped notches. Piston means can be used to urge the flaps to the extended position, and the tube can be provided with rearwardly-extending V-notched wings.

For the steering of projectiles solely by the action of the air stream, fins or similar steering means projecting from the projectile have in most cases been used. Projectiles of that kind are, as a rule, not suited for firing by weapons of the same calibre as the projectiles and provided with a stationary propelling charge. Therefore, it has recently been suggested to design projectiles with special steering surfaces at the outside thereof, for example in the form of conical, pointed members with a sharp rear edge and a constriction behind said sharp rear edge, said constriction having conical surfaces which, under the influence of the air stream, bring about a stabilization of the projectile in its path. It has been found to be of advantage to provide projectiles of that kind with a rearwardly directed, steering tube.

It has also been suggested to provide the middle part of such a steering tube with longitudinal slots and to shape the bars between said slots in such a way that they will be bent out to a certain extent under the action of the pressure of the propelling gases when the projectile is thrown out from the bore of the weapon. By this means, the action of the steering tube is improved. It is, however, by this construction, frequently diificult to give a non-rotating projectile or a slowly rotating projectile good steering in its path because of the difiiculty in locating the air pressure center of the projectile sufliciently far rearwardly on the projectile.

Said air pressure center is, in this connection, defined as the point of action of the resultant of the pressure forces which are acting on the steering surfaces of the projectile and which are generated because of the movement of the projectile relative to the air.

The present invention relates to a projectile with a rearwardly directed steering tube and has for an object to give the steering tube a special shape, by which the air pressure center will be located further in a rearwardly direction than in projectiles of hitherto known types, whereby the steering action of the steering tube will be improved and the projectile will be given a more efiiective and more reliable steering.

The .invention is characterized by the fact, that the steering tube is provided with two or more substantially longitudinal, evenly distributed, rearwardly open weakenings or slots, so that flaps are formed, two or more of said flaps being provided with substantially transverse Weakenings or slots which are formed with an outward Widening cross section, in such a way, that, when the projectile is thrown out from the firing tube of the weapon, the slots, under the action of the pressure from the propelling gases, are bent outward, and that the transverse weakenings thereby will be closed in such a way, when the bending angle of the flaps has reached a desired value, that a further out-bending of the flaps is rendered more difficult or prevented.

By the outbending of the flaps, a steering portion located at the rearmost end of the steering tube is formed, said steering portion having a considerably bigger diameter than the rest of the steering tube. The steering tube has, as a rule, only a slightly smaller width than the calibre of the projectile and, therefore, steering means are formed by said flaps which project far outside the biggest cross section of the projectile and also project outside the turbulent air layer which is nearest to the projectile and its steering tube. This is still more the case if the flaps are provided with longitudinal ribs or flanges which project behind the steering tube and serve as steering fins after the deformation.

It is of essential importance, in order to obtain an eflfective steering, that the steering flaps, which are bent out by the propelling gases, are bent out uniformly so that the steering tube also after the firing will maintain its symmetry.

In a steering tube according to the present invention this condition will be fulfilled by the simple arrangement that the flaps are provided with transversal weakeniiigs or indications. Thereby, the rest of the steering tu-be may be sufficiently rigid so that the deformation occurs only at said weakenings. The weakenings consist of grooves with an outward widening cross section, so that when the bending out of the flaps has reached the desired degree the grooves are tightened, so that a further outbending is prevented. The flaps are, however, so much weakened at said indications, that they are surely bent out by the gas pressure against said hindrance.

Other advantages and characteristics of the present invention will be evident from the following specification which describes some embodiments of the invention, references being had to the accompanying drawings.

FIG. 1 illustrates a side elevation of a steering tube provided with three longitudinal and three transversal slots.

FIG. 2 is a side elevation of a projectile with a steering tube fastened thereto, the steering tube being shown in longitudinal section, and after that it has been deformed when the projectile has been fired.

FIG. 3 illustrates the steering tube as seen from the rear end thereof, after the deformation.

FIG. 4 is a rear view of a steering tube according to an alternative embodiment, in which the fixed part of the steering tube as well as four flaps which are formed by means of four slots are provided with longitudinal ribs or flanges at the inside and the outside of the steering tube, said ribs or flanges being radially directed and forming projecting steering wings behind the steering tube.

FIG. 5 is a longitudinal section AA of the steering tube according to FIG. 4.

FIGS. 6 and 7 illustrate a steering tube intended for a rearwardly tapering projectile, said steering tube being provided with flanges and having a bottom provided with a central opening and a number of slots, so that six outwardly bendable bottom flaps with steering wings will be formed. FIG. 6 is a longitudinal section and FIG. 7 is an end section of said steering tube.

FIGS. 8 and 9 are a longitudinal section and an end elevation, respectively, of an embodiment of the invention in which six bottom flaps provided with steering wings are bent out rearwardly by means of a piston which is actuated by the gas pressure and which locks the flaps in their outbent positions.

The steering tube illustrated in FIG. 1 comprises a cylindrical, tubular member 1 which is open in both ends, and which at its front end is provided with a thread 2, by means of which it is fastened to the rear end of the projectile 3, as illustrated in FIG. 2. The rear end of the tube is provided with three longitudinal slots 4, said slots being open rearwardly and evenly distributed around the circumference of the steering tube. By means of said slots 4 three flaps 5 are formed at the rear end of the steering tube. Each of the flaps 5 is provided with a transversal slot 6 with a V-shaped cross section, the length of said slot being somewhat less than the width of the fiap at the base thereof, as illustrated in FIG. 2 and 3. By the slots 6 the steering tube is weakened at the base of each flap 5, so that the flap may be easily bent out. The remaining portions of material between the slots 6 and 4 form a sort of hinge for each flap. At the moment when the projectile leaves the muzzle of the weapon there will still be a gas pressure within the steering tube which is not counterbalanced by any outside pressure. Due to this fact, the flaps 5 will be pressed or bent out by the inner overpressure and, therefore, the steering tube will be deformed as illustrated in FIGS. 2 and 3. When the flaps 5 are bent out the slots 6 will be tightened until the side surfaces thereof or parts of said side surface will abut against each other. Thereafter, a further bending out of the flaps may be rendered more diflicult or entirely prevented.

By giving the slots or the weakenings a suitable shape, for example providing a rounding in the bottom of each slot, and by making the wall thickness of the steering tube variable with the distance from the rear end of the tube, the hinge for each fiap may be given a length and a shape and a rigidity just as desired. Further, the parts of the transversal slot or indication, which will be brought together when the flap is bent out, may be given a suitable shape so that the surfaces which will be abutting against each other may have a suitable shape and size. By this means, the condition for obtaining an efficient steering action, as indicated in the foregoing, may be fulfilled. By giving the longitudinal slots or indications a suitable shape, it is also possible to vary the form of the projecting flaps according to desire.

Some projectiles may require a more rigid steering tube. For that purpose it may be suitable to provide the rear end of the steering tube with a bottom which has a central opening and slots or weakenings going out from said central opening, said slots being of the same number as the longitudinal slots and going over in the latter. Be-

4 cause of the small opening rearward, the overpressure in the steering tube will be maintained a longer time after the exit of the projectile from the firing tube of the weapon and, therefore, the hinges of the flaps may be made more rigid.

In FIGS. 4 and 5 a cylindrical steering tube 7 is illustrated in which there are four longitudinal slots 8 and four flaps 9, the slots as well as the flaps being arranged in pairs, the two slots and the two flaps, respectively, belonging to one pair, being diarnmetrically opposite to each other. Opposite to and on each of said flaps inside as well as the outside of the steering tube is provided with a longitudinal, radially directed rib or flange 10, 11 which, behind each flap 9, forms an integral, rearwardly projecting disc 12. According to this embodiment, the X -shaped, transversal slots 13 are so shaped, that they, at the inner part thereof, are going over in V-shaped recesses 14 in the inside ribs 10 of the steering tube, whereby also said ribs are weakened to a suitable degree so that the flaps 9 may be bent out under the action of the propelling gases. When the flaps are bent out, the discs 12 will be folded out so that inclined rearwardly projecting steering fins 12 are formed, which is shown by dash-dotted lines in FIG. 5 Also in this case, the recesses 14 in the flanges will be tightened and prevent further bending out. These steering fins may be designed to reach out in the undisturbed air outside the projectile and effectively contribute to the steering of the projectile without causing such a great air resistance as the flaps 9 would do, if they were of a cor responding length.

The rearwardly projecting discs 12 of the steering tube according to this embodiment of the invention will be easily obtained if one makes the tube from a tubing which is profiled with inside and outside ribs, and removes a suit able part of the tube wall between the ribs at the rear end of the tube.

A somewhat modified embodiment will be obtained if the steering tube according to FIGS. 4 and 5 is made conical or tapering rearwardly. This will be of advantage, especially in such cases, where it is important to maintain an effective steering of the projectile and to decrease the air resistance. The outbent flaps 9 in such a conical steer ing tube will not reach outside the greatest cross section of the projectile, and, therefore, the breaking action of such flaps will be decreased in comparison with said breaking action if it is a cylindrical steering tube. Of course, also the steering action will be decreased, but the projectile will still get a good steering by means of the steering fins 12. Possibly, the air adjacent to said steering fins will be less disturbed by the outbent flaps if the steering tube is conical, and, therefore, their steering action will increase.

In FIGS. 6 and 7 there is an embodiment shown, in which the steering tube is provided with a slotted bottom according to the foregoing. The steering tube comprises a cylindrical tube 15 which is provided with a bottom 16 at the rear end of the tube. This bottom is provided with a central, circular opening 17 and it is also provided with evenly distributed slots so, that the bottom is divided into six equal flaps 19 by six slots going in radial directions from the opening, each flap having the shape of a truncated circle sector. The cylindrical part 15 of the steering tube is, at the rearmost end thereof, provided with six short, longitudinal slots 20, which are going over in the six bottom slots 18, so that the bottom flaps 19 go over in short flaps 21, which are formed by means of the slots 20. Somewhat in front of the inside of the bottom 16, the tube 15 is provided with six further transversal weakenings 22 which have a V-shaped cross section and are opened in an outward direction, the bottom of each slot forming a chord between two adjacent, longitudinal slots 20. Thus, said bottoms are forming a regular hexagon. Just opposite each of the flaps 19, the steering tube is provided, at the outside thereof, with a radially directed steering fin 23, 24 which is fastened to the cylindrical part of the steering tube as well as to its bottom, said steering fin extending along the steering tube and projecting rearwardly behind the latter. Each of the steering fins is provided with a V-shaped recess 25 located opposite the V-shaped recess 22 in the steering tube, said V-shaped recess 25 dividing the steering fin in one front portion 23 which is fastened to the steering tube and one rear portion 24 which is fastened to the bottom flap 19. A steering tube according to this embodiment is intended to be used on a projectile which is tapering rearwardly, and to be fastened to said projectile by means of a thread 26. When the projectile exits the firing tube of the weapon, the short flaps 21 will be bent outwardly by the remaining gas pressure in the steering tube and then also the bottom flaps 19 will be bent outwardly at an angle which is determined by the angle of the weakenings or recesses 22 of the steering tube and the recesses 25 of the steering wings, because the side surfaces of said recesses will strike against each other and prevent a further bending of the flaps 19.

In this embodiment, the air resistance caused by the outbent flaps will be decreased to a minimum and so will also the air disturbances adjacent to the steering fins, which is caused by the steering flaps, because a very short portion of the tube 15 is bent out and said portion will be located entirely within the calibre of the projectile.

For projectiles where the gas pressure is not suificient for the flaps to be outbent to the desired extent, in spite of the fact that the steering tube according to the last described embodiment is provided with bottom flaps, it may be necessary to weaken the flaps to such an extent that they will be insta-ble in the outbent position, and may be bent inwardly again by the pressure forces which are generated by the air stream, and in that case the flaps have to be locked in their outbent positions.

FIGS. 8 and 9 illustrate an embodiment of a steering tube according to the invention, in the rear part of which a piston, known per se, is provided. The piston is displaceable in a longitudinal direction of the Steering tube and is adapted to cooperate with the bottom flaps of the steering tube and, under the action of the driving gases, to bring about the bending out of the flaps with the steering wings against their stop positions and locking the flaps in that position. In addition to the locking of the flaps in the outbent position there will also be a greater pressure force acting on the flaps for outbending the latter.

The steering tube has substantially the same shape as the already described steering tubes apart from the fact, that the six bottom flaps 27 have a thickness which is increasing towards the center. There is a rearwardly directed tube 28 threaded into the rear end of the projectile, the outer mantle surface of said tube 28 forming a sliding and steering surface for a cup-shaped, rearwardly displaceable piston 29, which has a rearwardly directed, convex surface, and is provided with an opening of the same diameter as the tube 28. The rear end of the tube 28 is provided with a flange 30 which serves as a stopper for the piston 29 when the latter is displaced backwards. In front of and adjacent to the flange 30, the tube 28 is provided with an annular recess 32 in which an annular spring 33 is located. Before the firing, the rear end of the piston 29, which has a forwardly directed, concave surface, is abutting against the inner side of the bottom flaps 27 of the steering tube. Between the inner, cylindrical surface of the steering tube and a flange 34 at the front end of the piston, there is a narrow, an-

nular recess 35, and between the rear part of the projectile and the piston 29, there is a cavity 36,

When the projectile is fired, the propelling gases penetrate the slots, the annular recess 35 and through leakage openings between abutting surfaces into the cavity 36, whereby an over-pressure is generated in said cavity when the projectile leaves the firing tube. The piston 29, therefore, is displaced backwards, and thereby the bottom flaps 27 will slide against the piston and be bent out 6 against the stoppers which are obtained by the tightening of the recesses 37 in the fins 38, 39. In the end position, the annular spring 33 slides down into the annular recess 31 in the tube 28, and locks the piston, and also the bottom fiaps, in this position. If it should be necessary, the access of the propelling gases to the cavity 36 may be facilitated by providing of openings in the piston 29.

Also a steering tube which is not provided with bottom flaps may be provided with a piston which bends the flaps out and locks them in an outbent position. In that case, the piston may have a less pronounced cup-shape, and may be adapted to abut against the inner wall surface of the steering tube. The steering tube has an inner diameter which is continuously decreasing behind the transverse weakenings, i.e. it has an increasing wall thickness, and thereby the flaps will be forced outwardly by the piston when the piston, under the action of the gas pressure, is displaced backwards.

The invention may be modified in several different ways within the scope of the same. Thus, the steering tube may, of course, be provided with a different number of flaps than has been described in the foregoing. If there is a greater number of flaps, for example six, it may be advantageous to give the steering tube a hexagonal cross section. The steering tube may be provided with, for example, U-shaped weakenings instead of the V-shaped weakening described in the foregoing.

In certain cases, it may be of advantage to provide the steering tube with a conical bottom. It is also possible to let the transversal slots make an angle to the longitu- 1 dinal axis of the steering tube which is unequal to so that the flaps may be bent out obliquely, whereby the projectile is brought to rotate.

I claim:

1. A projectile having a rearwardly directed steering tube provided with a plurality of substantially longitudinal and uniformly spaced apart rearwardly directed slots dividing the rear portion of the tube into a plurality of flaps, a plurality of transverse slots extending transversely of the tube and located substantially in line with the inner ends of the longitudinal slots, each of the transverse slots being located at the base of each of the flaps, each of the transverse slots being defined by walls which diverge outwardly from the interior of the tube so that when the projectile leaves the firing tube of a weapon the flaps, under the action of the propelling gases, will be bent out on the line of the transverse slots and have their outward bending action limited by the closing of the transverse slots and the contact between the walls of said slots.

2. A projectile having a rearwardly directed steering tube provided on its exterior with a plurality of spaced apart, longitudinally extending, radially-disposed fins, said fins having parts extending rearwardly of the rear end of the tube, each of the fins having a V-shaped notch located adjacent to the rear end of the tube, the notches permitting the fins to be bent outwardly when the projectile is fired, but only to a limited extent controlled by contact between the walls of each V-shaped notch.

3. A projectile according to claim 2, characterized by the fact, that a piston is provided, said iston being displaceable in the longitudinal direction of the steering tube under the action of propelling gases which penetrate into the steering tube in front of said piston, and which generate a pressure, that remains after that the projectile has left the firing tube of the weapon, said piston being displaced backwards, and by pressing against the flaps of the steering tube, brings about an outbending of said flaps and, the V-notches being effective to limit the outthrust of the flaps under piston projection.

4. A projectile including a steering tube, flaps on said tube, a piston located forwardly of the flaps and provided with an axial opening extending through it, a tube attached to the rear portion of the projectile and directed rearwardly and entering and passing through the opening in the piston, the tube having a flange disposed beyond one end of the piston, the piston having an annular recess, the said flange limiting the rearward movement of the piston, an annular spring located in the recess, said spring being adapted to slide down into a part of the tube adjacent to the flange, which part is of smaller diameter than a part of the tube around which the piston is located, said spring being eflective when it enters said part of the tube to lock the piston against outward movement and control the outward projection of the flaps.

8 References Cited UNITED STATES PATENTS 1/1916 Alard 2443.29

2/1958 Hansen et a1. 2443.28

BENJAMIN A. BORCHELT, Primary Examiner.

SAMUEL W. ENGLE, Examiner.

V. R. PENDEGRASS, Assistant Examiner. 

1. A PROJECTILE HAVING A REARWARDLY DIRECTED STEERING TUBE PRIVIDED WITH A PLURALITY OF SUBSTANTIALLY LONGITUDINAL AND UNIFORMLY SPACED APART REARWARDLY DIRECTED SLOTS DIVIDING THE REAR PORTION OF THE TUBE INTO A PLURALITY OF FLAPS, A PLURALITY OF TRANSVERSE SLOTS EXTENDING TRANSVERSELY OF THE TUBE AND LOCATED SUBSTANTIALLY IN LINE WITH THE INNER ENDS OF THE LONGITUDINAL SLOTS, EACH OF THE TRANSVERSE SLOTS BEING LOCATED AT THE BASE OF EACH OF THE FLAPS, EACH OF THE TRANSVERSE SLOTS BEING DEFINED BY WALLS WHICH DIVERGE OUTWARDLY FROM THE INTERIOR OF THE TUBE SO THAT WHEN THE PROJECTILE LEAVES THE FIRING TUBE OF A WEAPON THE FLAPS, UNDER THE ACTION OF THE PROPELLING GASES, WILL BE BENT OUT ON THE LINE OF THE TRANSVERSE SLOTS AND HAVE THEIR OUTWARD BENDING ACTION LIMITED BY THE CLOSING OF THE TRANSVERSE SLOTS AND THE CONTACT BETWEEN THE WALLS OF SAID SLOTS, 